1. Field of the Invention
The present invention relates to electrical power systems and, more particularly, to arrangements for electrically interconnecting outlet receptacle blocks so as to provide for a selected one of a plurality of power supply circuits.
2. Background Art
The use of computers, associated computer peripherals (e.g. printers and the like), copiers, facsimile machines, sophisticated telecommunications equipment and other electronic devices is continuing to rapidly increase in commercial, industrial and office environments. As a result, the importance of efficiently supplying power throughout these environments is also increasing. For example, the use of modular office systems, with multiple workstations and interior walls, has led to electrical systems relatively more sophisticated than conventional designs comprising receptacle mounts and electrical receptacles in stationary walls, with the receptacles energized from incoming power supplies extending through wall interiors. Such conventional and stationary wall-mounted systems were often located a substantial distance from the electrical devices to be energized and numerous electrical cords connecting the devices to the outlets would cause unsightly and sometimes dangerous entanglements. Thereafter, movable pluggable units having a number of receptacles on a common power source cord to be plugged into the conventional utility outlets were used. Again, however, such units resulted in unsightly and entangled arrays of electrical device cords.
With the growth of the use of electrical power in office systems, it became known to employ removable wall panels or the like, which defined modular workplace areas. Further, raceway areas were developed for use in the panels or other structures, for accommodating electrical wiring and electrical junction blocks near the locations to be energized. Typically, junction blocks were mounted within the raceway areas by attaching them with various types of structural arrangements. Outlet receptacle blocks having a number of receptacles were first formed as an integral part of the junction blocks. Thereafter, it became known to employ receptacles which were assembled as devices separate from the junction blocks, but were mechanically and electrically connectable to the junction blocks. During the past two decades, a substantial amount of research and development have been directed to raceways, junction blocks and receptacles, means for interconnection of the junction blocks and receptacles, and mounting of the junction blocks within the raceways.
One aspect of the increasing use of electrical power relates to circuit loads. Any particular electrical circuit is limited to carrying a finite power load. Previously, when electrical power was not used to the extent that it is today, a single electrical circuit interconnecting to an incoming power supply was typically sufficient to handle power requirements. Accordingly, wiring within stationary or movable walls could comprise only two (hot and neutral) or three (hot, neutral and ground) wires, with receptacle blocks having single (simplex) or double (duplex) receptacles typically wired directly to the incoming two or three wire circuit. However, today, it is advantageous to employ systems having an incoming power supply comprising multiple electrical circuits.
Further, however, having the availability of multiple circuits has led to other electrical wiring issues. For example, a number of junction blocks and outlet receptacle blocks may be assembled within several raceways of a modular system, with wiring and bus bars configured for interconnection of the outlet receptacles to a particular one of the available multiple circuits. However, over time, electrical power loads may change, resulting in load balance problems and the like. These changes may require circuit reconfigurations involving substantial rewiring and “changeout” of junction blocks, receptacles and other electrical components to other devices having different wire and bus bar configurations to accommodate circuit changeovers.
Various circuit arrangements have been utilized in the recent past in an attempt to provide circuit selection. For example, McCarthy, U.S. Pat. No. 4,775,328, issued Oct. 4, 1988, discloses an electrical power assembly for installation in a raceway of a wall panel, of a type commonly used in modular wall systems for constructing office and other work areas. The McCarthy configuration includes a power block having seven wires, representing three separate circuits, and several ports for receiving different outlet receptacle adapters or modules. Different modules are utilized to connect a power cord or the like to the different circuits of the power block. Each of the ports of the power block has seven terminals, corresponding to the seven wires, and each of several outlet receptacle modules has a uniquely positioned set of three terminals for engaging a predetermined set of three of the seven power block terminals. In this manner, different outlet receptacle modules provide electrical connections to different ones of the three separate circuits. A disadvantage of this prior art arrangement is that a separate supply of receptacle modules must be kept, and a receptacle module of proper type must be found each time a change is to be made to a different circuit arrangement. This presents a substantial inconvenience to the user and requires a separate stocking of these parts.
Byrne, U.S. Pat. No. 5,087,207, issued Feb. 11, 1992, presented a substantial advance with respect to circuit selection. The Byrne arrangement utilized a pair of adapter blocks, each arrangeable in two physical orientations. These blocks provided an interface between an electrical outlet receptacle block and four different electrical circuits of a power distribution block. Each of the adapter blocks included terminals on one end for engaging the receptacle block, including one terminal disposed on the centerline of the adapter and a pair of terminals disposed on opposing sides and equidistant from the centerline. Further, each adapter block included terminals on an opposite end for engagement with the power distribution block. The adapter block also included terminals disposed on opposite sides of the centerline and offset from the centerline by different distances. Each adapter block could be changed from one physical orientation to another by rotation about the centerline. One of the blocks, in a first physical orientation, connected a first positive terminal, a first neutral terminal and a ground terminal of the power distribution block to the outlet receptacle block. In a second orientation, connection was made to a second one of the positive terminals, a second one of the neutral terminals and a ground terminal of the power distribution block to the outlet receptacle block. Correspondingly, the second adapter block, in a first physical orientation, connected a third positive terminal, a third neutral terminal and a ground terminal of the power distribution block to the outlet receptacle block. In a second physical orientation, the second adapter block connected a fourth positive terminal, a fourth neutral terminal and a ground terminal of the power distribution block to the outlet receptacle block.
Wilson et al, U.S. Pat. No. 4,367,370, issued Jan. 4, 1983, discloses an outlet receptacle block having a ground terminal, a common terminal and three positive terminals for engaging corresponding terminals of a junction block. The ground and common terminals are connected to the ground and common receptacle output terminals for engagement with the prongs of a standard three-prong electrical cord. The receptacle block further includes a switch which selectively connects one of the three positive prongs to the positive receptacle outlet connector, internal to the outlet receptacle block.
In another prior art arrangement in Tillmann, U.S. Pat. No. 4,666,223, issued May 19, 1987, an outlet receptacle block is provided with a movable terminal to selectively engage one of three positive junction block terminals. The outlet receptacle block of this prior art arrangement includes a conducting shaft electrically connected to the positive outlet terminal of the outlet receptacle block and to the movable terminal. The movable terminal may be slid upwardly or downwardly to a desired position for engagement with one of three positive connector terminals of the junction block.
In yet another prior art arrangement in Wilson et al, U.S. Pat. No. 4,781,609, issued Nov. 1, 1998, an outlet receptacle block is provided with a pair of slideable terminals mounted on a carrier so as to provide for synchronous movement of two contacts. A junction block is provided with a ground terminal, three positive terminals and three common terminals, thereby defining three separate circuits with a common ground. The carrier on the outlet receptacle block may be positioned so that one of its terminals engages one of the positive terminals of the junction block, while the other engages the corresponding common terminal. A sliding electrical contact internal to the receptacle block provides contact between the moveable terminals and corresponding terminals for engagement with the prongs of a standard electrical cord.
With several of the above-mentioned prior art arrangements, an electrical switch contact between a moveable part and a stationary part is employed to connect the outlet terminals of the outlet receptacle block.
Byrne, U.S. Pat. No. 5,096,431, issued Mar. 17, 1992, provided another substantial advance with an outlet receptacle block having rearrangeable terminals. In Byrne, an electrical outlet receptacle block comprises a housing and at least one flexible bus bar having one portion fixedly attached to the housing and electrically connected to one of the outlet receptacle terminals of the receptacle block. An end of the flexible bus bar is a moveable terminal end, which may be moved to at least two separate positions for selective alignment with different terminals of a junction block having at least two different circuits.
Byrne discloses one embodiment with an electrical junction block comprising eight terminals, with four positive terminals, two neutral terminals and two ground terminals. The outlet receptacle block is provided with three bus bars for connection to positive, neutral, and ground outlet terminals. The flexible bus bars may be selectively positioned to connect the ground outlet terminal to either of the two ground junction block terminals. In addition, the neutral outlet terminal can be connected to either of the two neutral junction block terminals, and the positive outlet terminal can be connect to any one of the four positive junction block terminals.
The outlet receptacle block can be provided with at least one manually operable control lever engaging the moveable end of at least one flexible bus bar. The housing of the receptacle outlet block is provided with an elongated slot on one surface for accommodating the control lever. The control lever can be disposed partially below the surface, with a protuberance extending through the slot. The protuberance is of a generally rectangular shape and fits snugly in the opening to prevent any significant rotation. The control lever, of which the protuberance is a part, is provided with an opening which engages a longitudinal section of a conductor bar. Movement of the control lever in the slot causes a bending in a portion of the control bar between the control lever and a fixed anchor point of the flexible bus bar internal to the receptacle outlet block housing. A terminal end portion of the bus bar extends beyond the control lever substantially perpendicular to an end wall of the receptacle block housing. This is provided for engagement with terminals of the junction block.